EP0448619B1 - Appareil de protection pour systemes electriques - Google Patents

Appareil de protection pour systemes electriques Download PDF

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Publication number
EP0448619B1
EP0448619B1 EP90900950A EP90900950A EP0448619B1 EP 0448619 B1 EP0448619 B1 EP 0448619B1 EP 90900950 A EP90900950 A EP 90900950A EP 90900950 A EP90900950 A EP 90900950A EP 0448619 B1 EP0448619 B1 EP 0448619B1
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EP
European Patent Office
Prior art keywords
local
ground fault
central
fault detector
current
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EP90900950A
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German (de)
English (en)
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EP0448619A1 (fr
Inventor
Dov Larom
Joseph Gross
Zohar Avrahami
Ram Suite 911 Tower 1 Silvercord Shalvi
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Solar Wide Industrial Ltd
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Solar Wide Industrial Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
    • H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
    • H02H3/334—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers with means to produce an artificial unbalance for other protection or monitoring reasons or remote control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned

Definitions

  • the present invention relates to an apparatus for protecting an electrical system against electrical shock in the event of a ground fault, and also for continuously monitoring the electrical system to assure it is operating in a proper and safe manner.
  • Electrical shock results from closing a current carrying loop through the body.
  • the loop consists of touching an electrical device which has a ground fault therein causing electrical current to flow through the body to ground.
  • the electrical current flowing through the body causes physiological effects which, depending on the intensity and time duration of the current, can be extremely hazardous and even fatal.
  • currents below 0.5mA usually produce no sensation or damage
  • currents from about 0.5 mA to about 16 mA commonly called the “let go threshold” generally produce a relatively weak electrical shock sufficient to produce sensation but insufficient to block the muscles so that the person receiving the shock may still "let go”
  • currents from 16 mA to about 50 mA may result in extreme pain, possible fainting, exhaustion injury, and paralysis of the muscles preventing the person from letting go
  • currents of above 50 mA may expose the person to ventricular fibrillation and death.
  • the current at first is very low because of the contact impedance which is very high at the instant of "touch” due to the low pressure applied, the small contact area, and the high skin resistance.
  • the current at this time may be below the perception threshold.
  • the contact area increases and the skin resistance decreases (the skin resistance being inversely proportional to the current), thereby increasing the current exponentially.
  • the electrical shock sensation produced may cause the person to release himself from the device if he reacts fast enough before the current has reached the "let go” threshold. If not, his reaction may be blocked, preventing himself from "letting go”.
  • One method of providing an electrical system with protection against electrical shock in the event of a ground fault is to include a ground fault detector and interrupter in the central mains inlet which detects leakage current to ground and interrupts the electrical system supplied from the central mains inlet.
  • a ground fault detector and interrupter in the central mains inlet which detects leakage current to ground and interrupts the electrical system supplied from the central mains inlet.
  • interrupters since such interrupters are applied to the central mains inlet and therefore serve a large number of electrical devices, their sensitivity cannot be any better than the inherent leakage of the overall system including all the local electrical devices connected to the system.
  • the starting currents for any of the electrical devices may be very high for short intervals, such that any slight imbalance in the system could actuate the interrupter.
  • transients during the starting of the device introduce high frequency components which also tend to actuate the interrupter.
  • the presently used ground fault detectors and interrupters are usually characterized by relatively poor sensitivity and reliability and/or a high rate of false interruptions
  • FRA 1489703 discloses an earth fault protection system with a central interrupter A and a local, more sensitive interrupter B.
  • the interrupter B is separately wire connected to the interrupter A to cause the interrupter A to be tripped whenever the interrupter B responds to a (low level) electrical fault in its output. This provides a system having effectively two levels of sensitivity but requiring additional wiring.
  • An object of the present invention is to provide a novel apparatus for providing an electrical system with protection against electrical shock in the event of a ground fault, and also for continuously monitoring the electrical system to assure it is operating in a proper and safe manner.
  • apparatus for providing an electrical system with protection against electrical shock in the event of a ground fault which electrical system supplies power from a central mains inlet to at least one local electrical device and which central mains inlet includes a central ground fault detector and central interrupter actuable upon detection of a first predetermined level of current imbalance to interrupt the central mains inlet
  • the apparatus comprising remote from said central ground fault detector a local ground fault detector for said at least one local electrical device supplied from the central mains inlet and actuable upon detecting, in its respective device, a current imbalance of a second predetermined level which is lower than said first predetermined level;
  • said local ground fault detector includes a local circuit interrupter actuable, upon detection of said second predetermined level of current imbalance, to interrupt the supply of current to the respective local electrical device, and a booster unit which increases a current imbalance at the local ground fault detector to a level greater than the first predetermined level and the increased imbalance being applied to the system at the local ground fault detector so that the central ground fault detector responds and said central interrupter
  • the connector could be the plug of the respective device, the socket for receiving the plug of the respective device, or an adaptor for receiving the plug of the respective device and for insertion into the socket of the respective device.
  • Each of the local ground fault detectors may be included in a local safety system which produces a visible indication, and also an audible alarm, upon its actuation.
  • the visible indication may be produced first, e.g., to alert the user that the device has a ground leak either before the user actually touches the device, or after touching but in time to let go.
  • the audible alarm may be actuated at the same time as the visible indicator, or preferably when a higher level of current imbalance is detected, to alert the person not to touch, or to let go if it is not too late, or at least to alert others in the area to come to the assistance of that person.
  • the sensitivity of the central interrupter is independent of the inherent leakage of the overall system or any particular electrical device in the system, since the central interrupter will automatically and quickly be actuated whenever any one of the local ground fault detectors is actuated.
  • the sensitivity of each local ground fault detector can thus be prefixed according to the characteristics of its respective local electrical device. The novel system thus permits high sensitivity and high reliability with a low rate of false interruptions.
  • the apparatus of the present invention may in particular be applied to existing systems already equipped with ground fault detector and interrupter, in which case it is only necessary to provide each of the local electrical devices with a local safety system including its own ground fault detector and the necessary connections to boost the fault current to the central interrupter, or otherwise to actuate the central interrupter, upon the actuation of any one of the local ground fault detectors.
  • the invention could be embodied in an overall comprehensive system also to include the central ground fault detector and interrupter actuated by any one of the local ground fault detectors.
  • the local safety system including its local ground fault detector can be conveniently included in the connector (plug, socket or special adaptor) for the respective local electrical device.
  • the local circuit interrupters could be included in existing systems, without central interrupters, to provide protection only with respect to individual local electrical devices, for example by incorporating the local safety system, including the visible and/or audible signals, with or without the local interrupter, in the connector for the local electrical device, e.g., in the socket, plug or adaptor for the local electrical device.
  • the electrical system includes a central mains inlet CMI comprising two mains conductors 2, 4 and a ground conductor 6, supplying electrical power to a plurality of local electrical devices LD 1 , LD 2 , LD 3 , etc., through a plurality of electrical sockets 8, 10, 12, one for each of the local electrical devices.
  • a central mains inlet CMI comprising two mains conductors 2, 4 and a ground conductor 6, supplying electrical power to a plurality of local electrical devices LD 1 , LD 2 , LD 3 , etc., through a plurality of electrical sockets 8, 10, 12, one for each of the local electrical devices.
  • the illustrated system is protected against electrical shock in the event of a ground fault by a central interrupter Cl which upon detecting a predetermined level of current imbalance interrupts the connection of the electrical system to the central mains inlet CMI.
  • the central interrupter Cl may be of conventional construction, e.g., of the differential transformer type, which measures the current flowing through mains conductor 2 in one direction, and the current flowing through mains conductor 4 in the opposite direction; in the event of an imbalance between the two of a predetermined magnitude, it actuates its interrupter to disconnect the electrical system from the central inlet CMI. Since such central interrupters are well-known, further details of their construction and operation are not set forth herein.
  • electrical systems protected only with a central interrupter are generally characterised by relatively low sensitivity or a high level of false interruptions since they are influenced by complete electrical system downstream of the interrupter.
  • they are preset so as to be actuated at a relatively low level of current imbalance, there will be relatively high rate of false interruptions; whereas if they are preset to be actuated at a relatively high level of current imbalance, they will be less sensitive to a fault in one of the local electrical devices.
  • each of the local electrical devices LD 1 , LD 2 , LD 3 , etc. with a local safety system including a local ground fault detector preset according to the characteristics of its respective local electrical device, so as to be actuatable upon detecting a current imbalance of a predetermined level, which is lower than the level at which the central and interrupter CI is actuated.
  • a local ground fault detector preset according to the characteristics of its respective local electrical device, so as to be actuatable upon detecting a current imbalance of a predetermined level, which is lower than the level at which the central and interrupter CI is actuated.
  • the central interrupter CI may therefore be set at a relatively high level, hereinafter called a first predetermined level, of current imbalance, and each of the local ground fault detectors may be preset so as to be actuated at a lower predetermined level, hereinafter called a second predetermined level, of current imbalance, depending on the specific characteristics of its respective local electrical device.
  • the local safety system including its local ground fault detector, may be incorporated in socket 8 (Fig. 1) for the respective local electrical device LD 1 , as illustrated by unit LSS in socket 8 in Fig. 1a.
  • it may be incorporated in the plug 14 of the respective local electrical device LD 2 , as indicated by unit LSS in plug 14 in Fig. 1b, or in a special adaptor as illustrated at 16 in Fig. 1c, including a plug 16a, connected to its respective electrical device LD 3 for insertion into the socket 10 (Fig. 1) for the respective electrical device.
  • Fig. 2 illustrates one form of local safety system LD2 which may be included in the connector to the respective local electrical device LD 1 -LD 3 to actuate the central interrupter CI upon detection of a current imbalance in the local electrical device.
  • each of the local safety systems LSS is adapted to detect a current imbalance of three different levels to perform different functions corresponding to the level of current imbalance detected
  • the central interrupter CI is adapted to interrupt the central mains inlet CMI when it detects another level of current imbalance, which latter level is higher than the three levels detected by each of the local safety systems.
  • threshold level TH 1 the highest level of current imbalance is indicated as threshold level TH 1 and as shown in Fig. 1, this level is detected by the central interrupter CI to interrupt the connection of the central mains inlet CMI to the electrical system supplying the power via conductors 2, 4 to the local electrical devices LD 1 -LD 3 , so that when this level of current imbalance is detected by the central interrupter CI, the complete electrical system supplied by the central mains inlet CMI is interrupted.
  • the central interrupter CI acts as a conventional central ground fault detector and interrupter presently used to protect electrical systems, except that the thresold level TH 1 for actuating the interrupter is preset at a substantially higher level than in the present conventional systems, to thereby reduce false interruptions without affecting sensitivity and reliability, since sensitivity and realibility are now determined by the local safety system LSS provided for each of the electrical devices LD 1 -LD 3 .
  • each of the local safety systems LSS includes a local ground fault detector LGFD capable of detecting three different levels of current imbalance, designated TH 2 , TH 3 and TH 4 respectively in Fig. 2.
  • the local ground fault detector LGFD outputs control signals TH 2 , TH 3 and TH 4 which are effective to perform the following functions:
  • the local ground fault detector LGFD for any one of the local electrical devices LD 1 -LD 3 detects a current imbalance of the second-largest threshold level TH 2 , it outputs a control signal to a booster unit BU which is effective to increase the current imbalance between the mains conductors 2, 4 connected to the central interrupter CI to the highest threshold level TH 1 , thereby causing the central interruptor to interrupt the supply of electrical power via the central mains inlet CMI to all the local electrical devices LD 1 -LD 3 .
  • control signal of threshold level TH 2 is also applied to a local interrupter LI also included in the local safety system unit LSS in the connector of the respective local electrical device LD 1 -LD 3 to interrupt the supply of electrical current to that electrical device.
  • the local ground fault detector LGFD for the respective local electrical device detects a current imbalance of the lower level TH 3 , it actuates an audible alarm unit AA to sound an alarm; and whenever it detects a current imbalance of the lowest level TH 4 , it energizes a visual indicator unit VI, which provides a visual indication of that level of current imbalance.
  • the lowest threshold level signal TH 4 would be preset to indicate to the user that the respective local electrical device has excessive leakage current, so that the person can be alerted to this condition and take appropriate protective or corrective measures.
  • the next highest threshold level signal TH 3 would be preset to actuate the audible alarm AA, not only to alert the person not to touch the "hot” device, or in time to cause him to let go if he has touched it, but in any event to alert those in the immediate vicinity of this condition in case the person can no longer let go.
  • the next highest threshold level signal TH 2 would be preset to actuate the booster unit BU to cause that unit sharply to increase the level of current imbalance in the electrical system to the highest threshold level TH 1 , so as to cause the central interrupter to immediately interrupt the current from the central mains inlet CMI.
  • Threshold level signal TH 2 will also be effective to actuate the local interrupter LI to interrupt the current supply to the respective local electrical device.
  • the threshold level TH 1 of the central interrupter can be set relatively high so that the central interrupter is not actuated by starting or transient conditions in the system but only when one of the local circuit interrupters is actuated.
  • the threshold levels of each local interrupter may be set according to the characteristics of the particular electrical device served by it. The threshold level of interruption of each local device should not be too low so that it would be actuated by starting or transient conditions, but the threshold level for actuating the visual and/or audible signals in the local safety system can be set quite low since their momentary actuation during starting or transient conditions would be recognized as such and could therefore be ignored.
  • Each local safety system LSS further includes a power supply unit PS which provides DC power to the various units in its respective local safety system.
  • Fig. 3 illustrates one form of local ground fault detector LGFD which may used in the local safety system of Fig. 2.
  • the detector includes a differential transformer DTR connected to the main conductors 2, 4, to sense any imbalance in the current through the two conductors and to produce an imbalance signal to an amplifier A.
  • the latter amplifier outputs the imbalance signal to three comparators CP 1 -CP 3 connected in parallel, each preset to output the three threshold control signals TH 2 -TH 4 according to the level of current imbalance.
  • control signals TH 2 -TH 4 exercise the various controls as described above with respect to Fig. 2.
  • differential transformer DTR which may be used in the local ground fault detector LGFD of Fig. 3 is illustrated in Fig. 4. It includes a high permeable core 20 having the mains conductors 2, 4, in the form of twisted wires, wound around two opposite legs of the core. The two remaining legs of the core include two sensing coils 22, 24. The sensing coils are mounted symmetrically on the core 20 and generate a voltage output proportional to the magnetic flux in the core.
  • the generated magnetic flux in the core is zero, and no voltage is induced in the sensing coils 22, 24.
  • the flux in the core is not zero but rather is proportional to the leakage current, and therefore the output voltage generated by the sensing coils 22, 24 would be proportional to the leakage current, i.e., to the current imbalance between the two mains conductors 2, 4.
  • the two mains conductors 2, 4 are preferably twisted to ensure symmetry and thus balance of the transformer; and sensing coils 22, 24 are symmetrical to reduce response to stray flux.
  • a magnetic shield 26 is preferably included to further reduce the response to stray flux.
  • the two sensing coils 22, 24 may be connected together in a parallel configuration, as illustrated in Fig. 4a, or in a series configuration, as illustrated in Fig. 4b.
  • the local ground fault detector illustrated in Fig. 3 further includes resistors Ra and Rb to produce an imbalance in the current when the "hot" wire 2 and the "neutral” wire are reversed and/or when the ground 6 is disconnected.
  • resistor Ra is connected between the hot wire 2 at the input end of the differential transformer DTR and the neutral wire 4 at the output end of the differential transformer; and resistor Rb is connected between the ground 6 and the hot wire 2-at the output end of the differential transformer. Both resistors are very high so as to provide a very small current therethrough.
  • Fig. 5 illustrates an example of a booster unit BU in the local safety system LSS of Fig. 2.
  • a booster unit BU in the local safety system LSS of Fig. 2.
  • Such a unit includes an electrical shunt circuit comprising the two resistors R 1 , R 2 supplied from the central mains conductors 2, 4, and an electrical switch SW 1 effective, upon receiving the threshold signal TH 2 from the local ground fault detector LGFD, to connect the shunt circuit to the ground circuit conductor 6 to thereby produce a large current imbalance, exceeding threshold level TH 1 (Fig. 1) sensed by the central interrupter CI.
  • This large current imbalance immediately actuates central interrupter CI to interrupt the current from the central mains inlet CMI to the electrical system.
  • Fig. 6 illustrates an example of a local interrupter LI which may be used in the local safety system LSS of Fig. 2.
  • the local interrupter LI is actuated by the same threshold control signal TH 2 as used for controlling the booster unit BU to actuate the central interrupter CI upon detecting a current imbalance of threshold level TH 2 .
  • the current to the local electrical device is interrupted at the same time with the interruption of the current to the whole electrical system supplied by the central mains inlet CMI.
  • the example of the local interrupter LI illustrated in Fig. 1 includes two fast fuses F 1 , F 2 , each in one of the mains conductors 2, 4. These fuses are blown when the threshold control signal TH 2 from the local ground fault detector LGFD (Fig. 2) is applied to one or both electronic switches Sw 2 , SW 3 . which short the mains conductors.
  • the surge current of the switches should be sufficiently high to ensure blowing the fuses, F 1 , F 2 , which thereby interrupts the supply of electrical current to the respective local electrical device.
  • the provision of two fast blowing fuses F 1 , F 2 , and two electronic switches SW 2 , SW 3 ensures that the circuit will be interrupted when the "hot" wire is not determined. When the "hot" wire is determined, one fuse and one switch would be adequate.
  • Fig. 6a illustrates another local interrupter circuit, therein designated LI', which may be used.
  • the control signal TH 2 is applied to a normally-closed fast-response latch-up relay or circuit-breaker RLY to interrupt the supply of current to the local electrical device.
  • Fig. 7 illustrates the audible alarm AA of Fig. 2 which is actuated by the threshold signal TH 3 generated by the respective local ground fault detector LGFD.
  • the threshold signal TH 3 is applied to a diode D 1 which controls an oscillator amplifier A 2 oscillating at an audio frequency.
  • diode b 1 conducts, and imposes a low impedance and low voltage at the positive input of oscillator amplifier A2, thus preventing it from oscillating.
  • diode D 1 is cut-off, whereupon amplifer A 2 oscillates at a frequency determined by R and C.
  • the output of the oscillator is supplied to a buzzer BUZ, e.g. a piezo-electric device, via voltage follower amplifer A 3 which acts as a buffer. Actuation of the buzzer BUZ produces an audible alarm indicating that a current imbalance corresponding to threshold level TH 3 has been detected in the respective local electrical device.
  • a buzzer BUZ e.g. a piezo-electric device
  • Fig. 8 illustrates a visual indicator VI which may be used in the local safety system LSS of Fig. 2 to indicate that the current imbalance, represented by the relatively low threshold level TH 4 , has been detected. This would indicate a relatively low level of leakage in the respective electrical device insufficient to interrupt the system but sufficiently to alert the user to take protective or corrective measures.
  • the visual indictor VI controlled by the threshold signal TH 4 via a switching transistor Q 1 may be an LE (light-emitting diode) which is energized when the control threshold signal TH 4 is detected.
  • Fig. 9 illustrates the power supply unit PS in the local safety system LSS of Fig. 2.
  • This unit includes resistor R 3 , a rectifier diode D 2 , for supplying DC to all the units in the respective local safety system illustrated in Fig. 2.
  • the system may be provided with the conventional central interrupter CI which is actuatable upon detecting a current imbalance in the mains conductors 2, 4 to interrupt the electrical system supplied by the central mains inlet CMI.
  • the central interrupter CI is preset so as to be actuatable at a relatively higher current imbalance indicated as threshold level TH 1 , than in the conventional systems, thereby minimizing false interruptions of the system, such as might be caused by starting or transient conditions.
  • Each of the local electrical devices LD 1 -LD 3 supplied by the central mains inlet CMI includes a local safety system LSS as illustrated in Fig.2.
  • the local safety system is incorporated in the connector of each local electrical device, as illustrated for example in the socket for the device as shown in Fig. 1a, in the plug for the device as sown in Fig. 1b, or in a special adaptor for the device as shown in Fig. 1c.
  • Each of the local safety systems LSS includes a local ground fault detector LGFD which measures the current imbalance, if any, in the respective electrical device, and outputs any one of three control signals TH 2 -TH 4 corresponding to the level of current imbalance detected.
  • control signal TH 4 which actuates the visual indicator VI. If a higher current imbalance is detected, it outputs control signal TH 3 which actuates the audible alarm AA; and if a still higher current imbalance is detected, it outputs control signal TH 2 which actuates the booster unit BU and also the local interrupter LI.
  • the visual indicator VI When the visual indicator VI is energized, this merely provides a visual indication of a potentially dangerous condition such as high leakage, so that the user can take appropriate protective measures if touching the quipment, or corrective measures to correct the condition.
  • the larger level of current imbalance represented by control signal TH3 sounds the audible alarm that there is a dangerous condition, to warn the user not to touch the equipment, or to "let go” if he can still do so after touching the equipment; this alarm also alerts those in the area in case the user needs assistance.
  • Control signal TH 2 which is outputted when the current imbalance now shows an extremely dangerous condition, automatically actuates booster unit BU to sharply increase the current imbalance in the overall system to the level TH 1 in order to immediately actuate the central interrupter CI, and thereby to disconnect the complete system from the central mains inlet CMI.
  • the local interrupter LI is actuated by control signal TH 2 to disconnect the respective local electrical device.
  • Both the visual indicator VI and the audible indicator AA may be of the non-latching type, so that the signals provided by them when sensing current imbalances of threshold levels TH 3 or TH 4 will continue only for the duration of the respective current imbalance; thus, if the current imbalance is caused by a starting or transient condition, the user will be alerted to this, but the condition will not actuate either the local circuit interrupter or the central circuit interrupter.
  • these threshold levels can be set relatively low as they will not result in a false interruption of the local electrical device or the central system.
  • the visual and audible indicators may be of the self-latching types, so that once actuated they remain actuated, thereby enabling any fault in the system to be easily traced.
  • a system could be provided only for protecting local electrical devices, e.g. by providing the above-described local safety system in individual local electrical devices, as by including the local safety system in the connector for the respective local electrical device.
  • a local safety system may be installed at the junction between the mains circuit and the extension, for example in a socket ( Figure 1a), and subsequent sockets may be wired to the "output" side of the socket so that any fault occurring in devices connected to the subsequent sockets will activate the local safety system.
  • Test and reset circuits may be provided for testing the main threshold level TH2.
  • the construction and operation of such circuits is well known in the art.
  • Very preferably a sense circuit is also provided, to enable the user to check that the lower threshold level(s), TH3 or TH4, is (are working, the audible or visible alarm being activated on testing with the sense circuit.
  • the main threshold level TH2 is set at about 7mAmp, and the or a lower threshold level is set at about 3.5mAmp, the sense circuit causing a leakage current just above the lower threshold level.
  • Both the visual indicator and the audible alarm may be arranged to be activated at a common lower threshold level, say 3.5mAmp. This may have particular advantage for people with sight or hearing impairment.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)

Claims (15)

  1. Appareil destiné à incorporer dans un système électrique une protection contre l'électrocution en cas de défaut à la terre, ce système électrique fournissant de l'énergie à au moins un dispositif électrique local (LDI) à partir d'une alimentation secteur centrale, et cette alimentation secteur centrale comprenant un détecteur de défaut à la terre central et un disjoncteur central (CI) qui peut être actionné sous l'effet de la détection d'un premier niveau prédéterminé de déséquilibre de courant. de façon à mette hors fonction l'alimentation secteur centrale, l'appareil comprenant, à distance du détecteur de défaut à la terre central, un détecteur de défaut à la terre local (8, 14. 16) pour le au moins un dispositif électrique local, alimenté à partir de l'alimentation secteur centrale et pouvant être actionné sous l'effet de la détection, dans son dispositif respectif, d'un déséquilibre de courant d'un second niveau prédéterminé qui est inférieur au premier niveau prédéterminé; caractérisé en ce que le détecteur de défaut à la terre local (8, 14, 16) comprend un disjoncteur local (LI) pouvant être actionné, sous l'effet de la détection du second niveau prédéterminé de déséquilibre de courant, de façon à interrompre la fourniture de courant au dispositif électrique local respectif (LED), et il comprend en outre une unité de renforcement (BU) qui augmente un déséquilibre de courant au détecteur de défaut à la terre local, jusqu'à un niveau supérieur au premier niveau prédéterminé, et le déséquilibre accru étant appliqué au système au détecteur de défaut à la terre local. de façon que le détecteur de défaut à la terre central réagisse et que le disjoncteur central (CI) interrompe le fonctionnement de l'alimentation secteur centrale, et en ce que chacun des éléments comprenant les détecteurs de défaut à la terre locaux (LGFD) et les disjoncteurs (LI) est inclus dans un système de sécurité local incorporé dans un connecteur (8, 14, 16) entre le dispositif électrique local respectif et le système électrique.
  2. Appareil selon la revendication 1, caractérisé en ce que le connecteur est une fiche d'alimentation (14) pour le dispositif électrique local respectif.
  3. Appareil selon la revendication 1, caractérisé en ce que le connecteur est une prise (8) destinée à recevoir une fiche du dispositif électrique local respectif.
  4. Appareil selon la revendication 1, caractérisé en ce que le connecteur est un adaptateur (16) destiné à recevoir la fiche du dispositif électrique local respectif et à être branché dans une prise pour le dispositif électrique local respectif.
  5. Appareil selon la revendication 1, caractérisé en ce que chaque détecteur de défaut à la terre local comprend en outre un moyen (VI) pour produire une indication visible lorsqu'il est actionné.
  6. Appareil selon la revendication 1, caractérisé en ce que chaque détecteur de défaut à la terre local comprend un moyen (AA) pour produire une alarme audible lorsqu'il est actionné.
  7. Appareil selon la revendication 1, caractérisé en ce que chaque détecteur de défaut à la terre local comprend un moyen (AA) pour produire une alarme audible lorsqu'il est actionné sous l'effet de la détection d'un second niveau prédéterminé de déséquilibre de courant, inférieur au premier niveau, et un moyen (VI) pour produire une indication visible sous l'effet de la détection d'un troisième niveau prédéterminé de déséquilibre de courant, inférieur au second niveau.
  8. Appareil selon la revendication 7, caractérisé en ce que le disjoncteur local comprend un interrupteur (SM2, SW3) connecté entre les conducteurs du secteur et pouvant être actionné pour court-circuiter les conducteurs du secteur sous l'effet de la détection du second niveau prédéterminé de déséquilibre de courant dans son dispositif respectif: et un fusible à action rapide (F1, F2) connecté aux conducteurs du secteur et adapté pour sauter de façon à ouvrir la connexion de l'alimentation secteur centrale au dispositif électrique local respectif, sous l'effet de l'actionnement de l'interrupteur.
  9. Appareil selon la revendication 1, caractérisé en ce que chacun des dispositifs électriques locaux comprend en outre un redresseur (figure 9) pour convertir le courant alternatif de l'alimentation secteur centrale en courant continu, pour fournir un courant continu à chaque détecteur de défaut à la terre local respectif.
  10. Appareil selon la revendication 1, caractérisé en ce que le détecteur de défaut à la terre local est actionné lorsque les fils de "phase" et de "neutre" sont inversés, et/ou lorsque le conducteur de terre est déconnecté.
  11. Appareil selon la revendication 1, caractérisé en ce que le détecteur de défaut à la terre local comprend un transformateur différentiel ayant un circuit magnétique (20) à perméabilité élevée ayant des branches opposées autour desquelles sont bobinés des conducteurs d'alimentation sous forme de fils, et dans lequel chacune des branches intermédiaires porte une bobine de détection (22, 24), pour produire une tension proportionnelle au flux magnétique dans le circuit magnétique.
  12. Appareil selon la revendication 11. caractérisé en ce que les conducteurs d'alimentation sont torsadés ensemble, l'un autour de l'autre, à l'endroit auquel ils entourent les branches du circuit magnétique.
  13. Appareil selon la revendication 11, caractérisé en ce que le détecteur de défaut à la terre local comprend un indicateur visible et une alarme audible, tous deux étant activés par le signal de commande, pratiquement au même niveau prédéterminé de déséquilibre de courant.
  14. Appareil selon la revendication 1, caractérisé en ce que le détecteur de défaut à la terre local comprend des moyens pour produire une indication visible et/ou une alarme audible sous l'effet de la détection d'un troisième niveau de déséquilibre, inférieur à la fois aux premier et second niveaux.
  15. Appareil selon la revendication 14, caractérisé en ce que le détecteur de défaut à la terre comprend des moyens de détection pouvant être actionnés par un utilisateur du système, pour faire en sorte que le troisième niveau de déséquilibre soit dépassé, pour confirmer ainsi que l'indication visible et/ou l'alarme audible peut fonctionner.
EP90900950A 1988-12-16 1989-12-18 Appareil de protection pour systemes electriques Expired - Lifetime EP0448619B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
IL88704A IL88704A (en) 1988-12-16 1988-12-16 Method and apparatus for protecting electrical systems
IL88704 1988-12-16
PCT/GB1989/001508 WO1990007214A1 (fr) 1988-12-16 1989-12-18 Procede et appareil de protection pour systemes electriques

Publications (2)

Publication Number Publication Date
EP0448619A1 EP0448619A1 (fr) 1991-10-02
EP0448619B1 true EP0448619B1 (fr) 1996-12-04

Family

ID=11059500

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90900950A Expired - Lifetime EP0448619B1 (fr) 1988-12-16 1989-12-18 Appareil de protection pour systemes electriques

Country Status (8)

Country Link
US (1) US5475557A (fr)
EP (1) EP0448619B1 (fr)
JP (1) JPH04504047A (fr)
AT (1) ATE146017T1 (fr)
AU (1) AU4821490A (fr)
DE (1) DE68927521D1 (fr)
IL (1) IL88704A (fr)
WO (1) WO1990007214A1 (fr)

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US6949934B1 (en) 2003-05-07 2005-09-27 Abb Technology Ag Fault-annuciating system for a transformer

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GB9813982D0 (en) * 1998-06-30 1998-08-26 Mem Limited Residual current detection device
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Also Published As

Publication number Publication date
US5475557A (en) 1995-12-12
IL88704A0 (en) 1989-07-31
WO1990007214A1 (fr) 1990-06-28
DE68927521D1 (de) 1997-01-16
ATE146017T1 (de) 1996-12-15
AU4821490A (en) 1990-07-10
EP0448619A1 (fr) 1991-10-02
IL88704A (en) 1992-02-16
JPH04504047A (ja) 1992-07-16

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